www.pudn.com > imgport.rar > jdsample.c, change:2008-11-05,size:16864b


/* 
 * jdsample.c 
 * 
 * Copyright (C) 1991-1996, Thomas G. Lane. 
 * This file is part of the Independent JPEG Group's software. 
 * For conditions of distribution and use, see the accompanying README file. 
 * 
 * This file contains upsampling routines. 
 * 
 * Upsampling input data is counted in "row groups".  A row group 
 * is defined to be (v_samp_factor * DCT_scaled_size / min_DCT_scaled_size) 
 * sample rows of each component.  Upsampling will normally produce 
 * max_v_samp_factor pixel rows from each row group (but this could vary 
 * if the upsampler is applying a scale factor of its own). 
 * 
 * An excellent reference for image resampling is 
 *   Digital Image Warping, George Wolberg, 1990. 
 *   Pub. by IEEE Computer Society Press, Los Alamitos, CA. ISBN 0-8186-8944-7. 
 */ 
 
#define JPEG_INTERNALS 
#include "jinclude.h" 
#include "jpeglib.h" 
 
 
/* Pointer to routine to upsample a single component */ 
typedef JMETHOD(void, upsample1_ptr, 
		(j_decompress_ptr cinfo, jpeg_component_info * compptr, 
		 JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)); 
 
/* Private subobject */ 
 
typedef struct { 
  struct jpeg_upsampler pub;	/* public fields */ 
 
  /* Color conversion buffer.  When using separate upsampling and color 
   * conversion steps, this buffer holds one upsampled row group until it 
   * has been color converted and output. 
   * Note: we do not allocate any storage for component(s) which are full-size, 
   * ie do not need rescaling.  The corresponding entry of color_buf[] is 
   * simply set to point to the input data array, thereby avoiding copying. 
   */ 
  JSAMPARRAY color_buf[MAX_COMPONENTS]; 
 
  /* Per-component upsampling method pointers */ 
  upsample1_ptr methods[MAX_COMPONENTS]; 
 
  int next_row_out;		/* counts rows emitted from color_buf */ 
  JDIMENSION rows_to_go;	/* counts rows remaining in image */ 
 
  /* Height of an input row group for each component. */ 
  int rowgroup_height[MAX_COMPONENTS]; 
 
  /* These arrays save pixel expansion factors so that int_expand need not 
   * recompute them each time.  They are unused for other upsampling methods. 
   */ 
  UINT8 h_expand[MAX_COMPONENTS]; 
  UINT8 v_expand[MAX_COMPONENTS]; 
} my_upsampler; 
 
typedef my_upsampler * my_upsample_ptr; 
 
 
/* 
 * Initialize for an upsampling pass. 
 */ 
 
METHODDEF(void) 
start_pass_upsample (j_decompress_ptr cinfo) 
{ 
  my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample; 
 
  /* Mark the conversion buffer empty */ 
  upsample->next_row_out = cinfo->max_v_samp_factor; 
  /* Initialize total-height counter for detecting bottom of image */ 
  upsample->rows_to_go = cinfo->output_height; 
} 
 
 
/* 
 * Control routine to do upsampling (and color conversion). 
 * 
 * In this version we upsample each component independently. 
 * We upsample one row group into the conversion buffer, then apply 
 * color conversion a row at a time. 
 */ 
 
METHODDEF(void) 
sep_upsample (j_decompress_ptr cinfo, 
	      JSAMPIMAGE input_buf, JDIMENSION *in_row_group_ctr, 
	      JDIMENSION in_row_groups_avail, 
	      JSAMPARRAY output_buf, JDIMENSION *out_row_ctr, 
	      JDIMENSION out_rows_avail) 
{ 
  my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample; 
  int ci; 
  jpeg_component_info * compptr; 
  JDIMENSION num_rows; 
 
  /* Fill the conversion buffer, if it's empty */ 
  if (upsample->next_row_out >= cinfo->max_v_samp_factor) { 
    for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components; 
	 ci++, compptr++) { 
      /* Invoke per-component upsample method.  Notice we pass a POINTER 
       * to color_buf[ci], so that fullsize_upsample can change it. 
       */ 
      (*upsample->methods[ci]) (cinfo, compptr, 
	input_buf[ci] + (*in_row_group_ctr * upsample->rowgroup_height[ci]), 
	upsample->color_buf + ci); 
    } 
    upsample->next_row_out = 0; 
  } 
 
  /* Color-convert and emit rows */ 
 
  /* How many we have in the buffer: */ 
  num_rows = (JDIMENSION) (cinfo->max_v_samp_factor - upsample->next_row_out); 
  /* Not more than the distance to the end of the image.  Need this test 
   * in case the image height is not a multiple of max_v_samp_factor: 
   */ 
  if (num_rows > upsample->rows_to_go)  
    num_rows = upsample->rows_to_go; 
  /* And not more than what the client can accept: */ 
  out_rows_avail -= *out_row_ctr; 
  if (num_rows > out_rows_avail) 
    num_rows = out_rows_avail; 
 
  (*cinfo->cconvert->color_convert) (cinfo, upsample->color_buf, 
				     (JDIMENSION) upsample->next_row_out, 
				     output_buf + *out_row_ctr, 
				     (int) num_rows); 
 
  /* Adjust counts */ 
  *out_row_ctr += num_rows; 
  upsample->rows_to_go -= num_rows; 
  upsample->next_row_out += num_rows; 
  /* When the buffer is emptied, declare this input row group consumed */ 
  if (upsample->next_row_out >= cinfo->max_v_samp_factor) 
    (*in_row_group_ctr)++; 
} 
 
 
/* 
 * These are the routines invoked by sep_upsample to upsample pixel values 
 * of a single component.  One row group is processed per call. 
 */ 
 
 
/* 
 * For full-size components, we just make color_buf[ci] point at the 
 * input buffer, and thus avoid copying any data.  Note that this is 
 * safe only because sep_upsample doesn't declare the input row group 
 * "consumed" until we are done color converting and emitting it. 
 */ 
 
METHODDEF(void) 
fullsize_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr, 
		   JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr) 
{ 
  *output_data_ptr = input_data; 
} 
 
 
/* 
 * This is a no-op version used for "uninteresting" components. 
 * These components will not be referenced by color conversion. 
 */ 
 
METHODDEF(void) 
noop_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr, 
	       JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr) 
{ 
  *output_data_ptr = NULL;	/* safety check */ 
} 
 
 
/* 
 * This version handles any integral sampling ratios. 
 * This is not used for typical JPEG files, so it need not be fast. 
 * Nor, for that matter, is it particularly accurate: the algorithm is 
 * simple replication of the input pixel onto the corresponding output 
 * pixels.  The hi-falutin sampling literature refers to this as a 
 * "box filter".  A box filter tends to introduce visible artifacts, 
 * so if you are actually going to use 3:1 or 4:1 sampling ratios 
 * you would be well advised to improve this code. 
 */ 
 
METHODDEF(void) 
int_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr, 
	      JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr) 
{ 
  my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample; 
  JSAMPARRAY output_data = *output_data_ptr; 
  register JSAMPROW inptr, outptr; 
  register JSAMPLE invalue; 
  register int h; 
  JSAMPROW outend; 
  int h_expand, v_expand; 
  int inrow, outrow; 
 
  h_expand = upsample->h_expand[compptr->component_index]; 
  v_expand = upsample->v_expand[compptr->component_index]; 
 
  inrow = outrow = 0; 
  while (outrow < cinfo->max_v_samp_factor) { 
    /* Generate one output row with proper horizontal expansion */ 
    inptr = input_data[inrow]; 
    outptr = output_data[outrow]; 
    outend = outptr + cinfo->output_width; 
    while (outptr < outend) { 
      invalue = *inptr++;	/* don't need GETJSAMPLE() here */ 
      for (h = h_expand; h > 0; h--) { 
	*outptr++ = invalue; 
      } 
    } 
    /* Generate any additional output rows by duplicating the first one */ 
    if (v_expand > 1) { 
      jcopy_sample_rows(output_data, outrow, output_data, outrow+1, 
			v_expand-1, cinfo->output_width); 
    } 
    inrow++; 
    outrow += v_expand; 
  } 
} 
 
 
/* 
 * Fast processing for the common case of 2:1 horizontal and 1:1 vertical. 
 * It's still a box filter. 
 */ 
 
METHODDEF(void) 
h2v1_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr, 
	       JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr) 
{ 
  JSAMPARRAY output_data = *output_data_ptr; 
  register JSAMPROW inptr, outptr; 
  register JSAMPLE invalue; 
  JSAMPROW outend; 
  int inrow; 
 
  for (inrow = 0; inrow < cinfo->max_v_samp_factor; inrow++) { 
    inptr = input_data[inrow]; 
    outptr = output_data[inrow]; 
    outend = outptr + cinfo->output_width; 
    while (outptr < outend) { 
      invalue = *inptr++;	/* don't need GETJSAMPLE() here */ 
      *outptr++ = invalue; 
      *outptr++ = invalue; 
    } 
  } 
} 
 
 
/* 
 * Fast processing for the common case of 2:1 horizontal and 2:1 vertical. 
 * It's still a box filter. 
 */ 
 
METHODDEF(void) 
h2v2_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr, 
	       JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr) 
{ 
  JSAMPARRAY output_data = *output_data_ptr; 
  register JSAMPROW inptr, outptr; 
  register JSAMPLE invalue; 
  JSAMPROW outend; 
  int inrow, outrow; 
 
  inrow = outrow = 0; 
  while (outrow < cinfo->max_v_samp_factor) { 
    inptr = input_data[inrow]; 
    outptr = output_data[outrow]; 
    outend = outptr + cinfo->output_width; 
    while (outptr < outend) { 
      invalue = *inptr++;	/* don't need GETJSAMPLE() here */ 
      *outptr++ = invalue; 
      *outptr++ = invalue; 
    } 
    jcopy_sample_rows(output_data, outrow, output_data, outrow+1, 
		      1, cinfo->output_width); 
    inrow++; 
    outrow += 2; 
  } 
} 
 
 
/* 
 * Fancy processing for the common case of 2:1 horizontal and 1:1 vertical. 
 * 
 * The upsampling algorithm is linear interpolation between pixel centers, 
 * also known as a "triangle filter".  This is a good compromise between 
 * speed and visual quality.  The centers of the output pixels are 1/4 and 3/4 
 * of the way between input pixel centers. 
 * 
 * A note about the "bias" calculations: when rounding fractional values to 
 * integer, we do not want to always round 0.5 up to the next integer. 
 * If we did that, we'd introduce a noticeable bias towards larger values. 
 * Instead, this code is arranged so that 0.5 will be rounded up or down at 
 * alternate pixel locations (a simple ordered dither pattern). 
 */ 
 
METHODDEF(void) 
h2v1_fancy_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr, 
		     JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr) 
{ 
  JSAMPARRAY output_data = *output_data_ptr; 
  register JSAMPROW inptr, outptr; 
  register int invalue; 
  register JDIMENSION colctr; 
  int inrow; 
 
  for (inrow = 0; inrow < cinfo->max_v_samp_factor; inrow++) { 
    inptr = input_data[inrow]; 
    outptr = output_data[inrow]; 
    /* Special case for first column */ 
    invalue = GETJSAMPLE(*inptr++); 
    *outptr++ = (JSAMPLE) invalue; 
    *outptr++ = (JSAMPLE) ((invalue * 3 + GETJSAMPLE(*inptr) + 2) >> 2); 
 
    for (colctr = compptr->downsampled_width - 2; colctr > 0; colctr--) { 
      /* General case: 3/4 * nearer pixel + 1/4 * further pixel */ 
      invalue = GETJSAMPLE(*inptr++) * 3; 
      *outptr++ = (JSAMPLE) ((invalue + GETJSAMPLE(inptr[-2]) + 1) >> 2); 
      *outptr++ = (JSAMPLE) ((invalue + GETJSAMPLE(*inptr) + 2) >> 2); 
    } 
 
    /* Special case for last column */ 
    invalue = GETJSAMPLE(*inptr); 
    *outptr++ = (JSAMPLE) ((invalue * 3 + GETJSAMPLE(inptr[-1]) + 1) >> 2); 
    *outptr++ = (JSAMPLE) invalue; 
  } 
} 
 
 
/* 
 * Fancy processing for the common case of 2:1 horizontal and 2:1 vertical. 
 * Again a triangle filter; see comments for h2v1 case, above. 
 * 
 * It is OK for us to reference the adjacent input rows because we demanded 
 * context from the main buffer controller (see initialization code). 
 */ 
 
METHODDEF(void) 
h2v2_fancy_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr, 
		     JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr) 
{ 
  JSAMPARRAY output_data = *output_data_ptr; 
  register JSAMPROW inptr0, inptr1, outptr; 
#if BITS_IN_JSAMPLE == 8 
  register int thiscolsum, lastcolsum, nextcolsum; 
#else 
  register JPEG_INT32 thiscolsum, lastcolsum, nextcolsum; 
#endif 
  register JDIMENSION colctr; 
  int inrow, outrow, v; 
 
  inrow = outrow = 0; 
  while (outrow < cinfo->max_v_samp_factor) { 
    for (v = 0; v < 2; v++) { 
      /* inptr0 points to nearest input row, inptr1 points to next nearest */ 
      inptr0 = input_data[inrow]; 
      if (v == 0)		/* next nearest is row above */ 
	inptr1 = input_data[inrow-1]; 
      else			/* next nearest is row below */ 
	inptr1 = input_data[inrow+1]; 
      outptr = output_data[outrow++]; 
 
      /* Special case for first column */ 
      thiscolsum = GETJSAMPLE(*inptr0++) * 3 + GETJSAMPLE(*inptr1++); 
      nextcolsum = GETJSAMPLE(*inptr0++) * 3 + GETJSAMPLE(*inptr1++); 
      *outptr++ = (JSAMPLE) ((thiscolsum * 4 + 8) >> 4); 
      *outptr++ = (JSAMPLE) ((thiscolsum * 3 + nextcolsum + 7) >> 4); 
      lastcolsum = thiscolsum; thiscolsum = nextcolsum; 
 
      for (colctr = compptr->downsampled_width - 2; colctr > 0; colctr--) { 
	/* General case: 3/4 * nearer pixel + 1/4 * further pixel in each */ 
	/* dimension, thus 9/16, 3/16, 3/16, 1/16 overall */ 
	nextcolsum = GETJSAMPLE(*inptr0++) * 3 + GETJSAMPLE(*inptr1++); 
	*outptr++ = (JSAMPLE) ((thiscolsum * 3 + lastcolsum + 8) >> 4); 
	*outptr++ = (JSAMPLE) ((thiscolsum * 3 + nextcolsum + 7) >> 4); 
	lastcolsum = thiscolsum; thiscolsum = nextcolsum; 
      } 
 
      /* Special case for last column */ 
      *outptr++ = (JSAMPLE) ((thiscolsum * 3 + lastcolsum + 8) >> 4); 
      *outptr++ = (JSAMPLE) ((thiscolsum * 4 + 7) >> 4); 
    } 
    inrow++; 
  } 
} 
 
 
/* 
 * Module initialization routine for upsampling. 
 */ 
 
GLOBAL(void) 
jinit_upsampler (j_decompress_ptr cinfo) 
{ 
  my_upsample_ptr upsample; 
  int ci; 
  jpeg_component_info * compptr; 
  boolean need_buffer, do_fancy; 
  int h_in_group, v_in_group, h_out_group, v_out_group; 
 
  upsample = (my_upsample_ptr) 
    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, 
				SIZEOF(my_upsampler)); 
  cinfo->upsample = (struct jpeg_upsampler *) upsample; 
  upsample->pub.start_pass = start_pass_upsample; 
  upsample->pub.upsample = sep_upsample; 
  upsample->pub.need_context_rows = FALSE; /* until we find out differently */ 
 
  if (cinfo->CCIR601_sampling)	/* this isn't supported */ 
    ERREXIT(cinfo, JERR_CCIR601_NOTIMPL); 
 
  /* jdmainct.c doesn't support context rows when min_DCT_scaled_size = 1, 
   * so don't ask for it. 
   */ 
  do_fancy = cinfo->do_fancy_upsampling && cinfo->min_DCT_scaled_size > 1; 
 
  /* Verify we can handle the sampling factors, select per-component methods, 
   * and create storage as needed. 
   */ 
  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components; 
       ci++, compptr++) { 
    /* Compute size of an "input group" after IDCT scaling.  This many samples 
     * are to be converted to max_h_samp_factor * max_v_samp_factor pixels. 
     */ 
    h_in_group = (compptr->h_samp_factor * compptr->DCT_scaled_size) / 
		 cinfo->min_DCT_scaled_size; 
    v_in_group = (compptr->v_samp_factor * compptr->DCT_scaled_size) / 
		 cinfo->min_DCT_scaled_size; 
    h_out_group = cinfo->max_h_samp_factor; 
    v_out_group = cinfo->max_v_samp_factor; 
    upsample->rowgroup_height[ci] = v_in_group; /* save for use later */ 
    need_buffer = TRUE; 
    if (! compptr->component_needed) { 
      /* Don't bother to upsample an uninteresting component. */ 
      upsample->methods[ci] = noop_upsample; 
      need_buffer = FALSE; 
    } else if (h_in_group == h_out_group && v_in_group == v_out_group) { 
      /* Fullsize components can be processed without any work. */ 
      upsample->methods[ci] = fullsize_upsample; 
      need_buffer = FALSE; 
    } else if (h_in_group * 2 == h_out_group && 
	       v_in_group == v_out_group) { 
      /* Special cases for 2h1v upsampling */ 
      if (do_fancy && compptr->downsampled_width > 2) 
	upsample->methods[ci] = h2v1_fancy_upsample; 
      else 
	upsample->methods[ci] = h2v1_upsample; 
    } else if (h_in_group * 2 == h_out_group && 
	       v_in_group * 2 == v_out_group) { 
      /* Special cases for 2h2v upsampling */ 
      if (do_fancy && compptr->downsampled_width > 2) { 
	upsample->methods[ci] = h2v2_fancy_upsample; 
	upsample->pub.need_context_rows = TRUE; 
      } else 
	upsample->methods[ci] = h2v2_upsample; 
    } else if ((h_out_group % h_in_group) == 0 && 
	       (v_out_group % v_in_group) == 0) { 
      /* Generic integral-factors upsampling method */ 
      upsample->methods[ci] = int_upsample; 
      upsample->h_expand[ci] = (UINT8) (h_out_group / h_in_group); 
      upsample->v_expand[ci] = (UINT8) (v_out_group / v_in_group); 
    } else 
      ERREXIT(cinfo, JERR_FRACT_SAMPLE_NOTIMPL); 
    if (need_buffer) { 
      upsample->color_buf[ci] = (*cinfo->mem->alloc_sarray) 
	((j_common_ptr) cinfo, JPOOL_IMAGE, 
	 (JDIMENSION) jround_up((long) cinfo->output_width, 
				(long) cinfo->max_h_samp_factor), 
	 (JDIMENSION) cinfo->max_v_samp_factor); 
    } 
  } 
}